So I've been doing a lot of research and finally started tuning my car. Disabled lean spool and have been leaning it out myself. I've got a good idea on what to do, I'm running RON98 and trying to hold around 12.5 on spool up and taper to 11.8ish at peak boost.

One thing I'm still not entirely sure on is when to worry about knock. I took 3 logs which are attached, and in the first there was 3 counts of knock, then in the next two there was none at the same point. So 3 is that threshold that everyone says is significant, but since it was not present in the other two pulls do I just ignore it? Was it therefore phantom knock?

 

Drop your timing a degree from 4200-4800 and hold that 11.1:1 AFR to redline. You're pushing it too hard for the gas you have. The peak load timing is causing the knock but that's too lean to safely run it hard and it has little benefit to power vs. timing. It's all up to you.

 

I wouldn't say that 11.9 is pushing too hard for RON98, but I do plan to drop it slightly, still in the process.
I don't want to run 11.1 that is way too rich for 98. I'm aiming for between 11.5 and 12 from peak load upwards.
So are you saying that the knock is an issue, despite the fact that it did not show up on the next two pulls?

 

Is it on a built block? Most cause a lot of noise that can set it off, I know mine does but haven't messed with adjusting the sensitivity.

 

Nope stock block, haven't adjusted sensitivity. I'm not worried about it because its easy to address and I'm not absolutely set on using those numbers. I just want to get an idea of whether this knock should be addressed, seeing as it didn't show up in consecutive pulls.

 

What boost are you running? 23-24psi?
Drop timing to 2* at 3500, 3* at 4250, 4* by 4750 and 5* by 5500 and see if that cures the knock.

On our 98 i've found little to no power difference between 11.3-11.8, I usually target 11.5-6 midrange and drop to 11.3 above 6500.

 

I'm running 25psi peak, dropping to around 22 by redline. I will richen up that area but no one has answered the question I have asked yet. Is the knock an issue if it didn't show up on the next two pulls?

 

At 8 Deg advance on 24psi I see some 4 Deg at times

 

I am not an expert on this, but have read lots of the gurus posts over the years. The way I tuned my setup is very conservative. If knock showed up once then it could show up again, and if you consider the data valid you need to address it until it doesn't show up in any of your testing. What the other posters are trying to tell is that it just takes one pull to go off the farm, and the engine can pop something.

Essentially it only takes once, so I tune against the once. I also have knock that is likely not completely real, but I can't prove or disprove that (I have deleted the balance shafts and since then knock is not as meaningful a data element).

However I still tune in a manner where if 3 pulls, and one pull has the knock I tune to get that knock out. I also track my car so the example would be. I run 12 laps, but it only takes lap #6 on the straight away to blow my engine. It didn't need to knock all of the laps.

Another way to think about it is to go conservative as you start to tune and learn, and then turn up the heat, values, power. As you get better you should measure your results with another tool to quantify the differences. Virtual Dyno software is pretty good at giving you deltas, so you could later on decide to push the timing another couple of degrees and see if it nets you any power. or power curve. If not its not worth the risk or bleeding edge map.


Good luck.

 

I would drop timing 1* to 2* a liittle and maybe put it a little bit richer above 4500 RPM maybe get the afr down to 11.1-11.3

 

Going rich (i.e. 11:1) leaves more endgas in the cylinder on cars without good VE and will increase the likelihood of knock. Running an 11.8-12.2 will work better. 98 RON is 93 US so he has plenty of octane for what he is attempting to do.

Going rich on spool can go both ways, again it depends on backpressure and VE of the combo. Your timing looks conservative right now so I wouldnt worry about that. I'd need to see a full log with knock voltage but I would presume you have a little phantom knock going on. You can check this with a fresh plug change and then look for peppering. Shut the car down immediately after the pull and pop plugs.

 

How good is your exhaust though?
In my experience, the 98 octane here needs to be around 1-2* from 3250-4250 at 24+psi of boost to not run into the odd knock even here and there.
Don't forget you don't want to be close to the limit as it will sporadically knock with changes in weather, fuel etc.

Yes JB, I do agree with poor VE it won't help hence the exhaust question, we more of a testing line to see how the combination reacts without knowing the intake/exhaust setup on the car.

To answer the OP question, yes I believe it is knock at that timing/boost combo on a stock turbo, go do 4-5 back to back pulls from 2-5k at this level, then pull 2* across the board from 200 load up, smooth back to 160 load and do another 4-5 pulls and compare notes.